1. Field of the Invention
This invention relates to dynamic magnet systems, and more particularly to magnetic transducers using ferrofluid bearings at the opposite ends of the magnets.
2. Description of the Related Art
Moving a magnet through a conductive coil induces a current flow in the coil. If the magnet is moved back and forth in a reciprocating motion, the direction of current flow in the coil will be reversed for each successive traverse, yielding an AC current.
Several electrical generating systems have been disclosed that make use of reciprocating magnet movement through one or more coils. For example, in various embodiments of U.S. Pat. No. 5,347,185, one, two or three rare earth magnets are positioned to move linearly back and forth relative to one or more coils. The magnets can either be fixed and the coil moved up and down relative to the magnet, as by wave action, the coil can be fixed and the magnet moved relative to the coil as by pneumatic pressure, or the coil housing can be shaken or vibrated as by being carried by a jogger, to cause a reciprocating or oscillating motion of a magnet which moves within the coil. In one embodiment four magnets are provided in successive polar opposition, with the two end magnets fixed and the middle magnets free to move back and forth along respective portions of a tube. The two middle magnets are separated from each other by the carrier for a middle coil, the carrier being approximately twice as wide as either of the middle magnets.
In U.S. Pat. No. 4,260,901, wave motion in a body of water causes a float to move up and down, which in turn imparts a reciprocating motion to a magnet that travels between a pair of coils stationed at opposite ends of its path. In U.S. Pat. No. 5,347,186, a rare earth magnet and a coil are positioned to move linearly back and forth relative to each other. The magnet can either be fixed and the coil moved up and down relative to the magnet, as by wave action, the coil fixed and the magnet moved relative to the coil as by pneumatic pressure, or the coil housing shaken or vibrated, as by being carried by a jogger, to cause a reciprocating motion of a magnet which moves within the coil.
In U.S. Pat. No. 5,818,132, a moving magnet is confined to a bi-directional linear or near linear motion through each of at least two mutually spaced coils for providing power in applications such as long life flashlights, alarm systems, communication devices located at places where conventional electric power sources are unavailable, and relatively high power repetitive forces such as the forces on the heel of a shoe during walking or running. One embodiment discloses three moving magnets that are suspended within a vertical tube in polar opposition to each other and to end magnets, with a number of coils spaced along the outside of the tube. To minimize friction between the moving magnets and the tube, the tube is oriented vertically and moved up and down to move the magnets relative to the coils, thus generating currents in the coils. However, the vertical orientation interferes with the motion of the magnets, which have to fight gravitational forces in order to move relative to the tube. The coupling of tube movements into the magnets is thus reduced.